A diesel particulate filter (DPF) which is disposed in an exhaust passage of a diesel engine for trapping particulate matter becomes clogged, as it continues to trap particulate matter. When a considerable amount of particulate matter has been deposited in the DPF, the DPF has to be regenerated. The regeneration is accomplished by forcibly burning the deposited particulate matter in the filter by raising the exhaust gas temperature.
JP2002-371900A published by the Japan Patent Office in 2002, proposes causing a fuel injector of the diesel engine to perform a post fuel injection, following a main fuel injection, in a crank angle range of 20 to 45 degrees before exhaust top dead center of a piston which corresponds to the later portion of the exhaust stroke. Then aim of this prior art is to burn the deposited particulate matter in the DPF using a heat generated by after-burning of the fuel injected in the post injection.